He was riding behind the Prophet ﷺ when a man came to him and said, "Messenger of Allah, my mother is a very old woman. If I mount her on a camel, she cannot hold on, and if I tie her, I fear I will kill her."The Messenger of Allah ﷺ replied, "Tell me, if your mother had a debt, would you pay it off for her?"The man said, "Yes."He said, "Then perform the pilgrimage on behalf of your mother."
أخبرنا أحمد بن سليمان قال حدثنا يزيد وهو ابن هارون قال أنبأنا هشام عن محمد عن يحيى بن أبي إسحق عن سليمان بن يسار
أنه كان رديف النبي ﷺ فجاءه رجل فقال يا رسول الله إن أمي عجوز كبيرة وإن حملتها لم تستمسك وإن ربطتها خشيت أن أقتلها فقال رسول الله ﷺ أرأيت لو كان على أمك دين أكنت قاضيه قال نعم قال فحج عن أمك
Sourcing, [sahih] Ahmad narrated it, 1/212, from the hadith of Yahya, in this manner, and it is in Kubra, hadith no. 3623. Muhammad is Ibn Sirin, and Hisham is Ibn Hassan, and he used the term "an" (indicating a possible break in the chain), but his hadith has corroborating narrations.